I. Field of the Invention
The present invention relates to an apparatus for enlarging or reducing the size of an image pattern such as a character or graphic pattern and, more particularly, to an apparatus suitable for normalizing an image pattern into a pattern of a predetermined size when data representing a feature of the image pattern to be recognized is compared with a set of reference data in an image recognition apparatus.
II. Description of the Prior Art
A conventional image recognition apparatus for recognizing an image such as a character or any other graphic pattern is designed to digitally process the image by using an electronic technique. An image to be recognized is processed by, e.g., vector analysis to obtain data representing a feature of the image. The feature data is compared with a set of reference data stored in a data base to determine by correlation calculations which reference data matches with the feature data more than the others, so that the image is specified with the most matching reference data.
In this case, however, the size of the image to be recognized is indefinite. For instance, when images are characters, they vary in size whether they are printed or handwritten characters. In a character recognition process, a character to be recognized is read with an image sensor and converted into digital data, which is then stored in a memory. Feature data of the character is prepared on the basis of the digital data stored in the memory to be compared with a set of reference data, each of which is feature data prepared for each character normalized in a predetermined size.
In this conventional process, the feature data obtained from the character to be recognized is prepared in accordance with the size of the character while the set of the reference data to be compared with the above feature data have been derived from characters having a normalized size. Therefore, when the size of the character to be recognized is different from the normalized size, the correlation calculation often results in nonmatching even when the character to be recognized is the same as that represented by one of the set of the reference data.
In order to solve this problem, the character to be recognized must be enlarged or reduced so as to be normalized to the same size as that of the characters represented by the set of the reference data, and feature data must be derived on the basis of the normalized character to be recognized.
In a conventional method for enlarging or reducing written characters, the plane including a written character is scanned in proper directions, for instance, in the horizontal, vertical, 45.degree. and 135.degree. directions. The initial and last intersecting points of each scanning line with the character are detected, and thereby peripheral points of the character are found. The whole size and the center position of the character are then determined according to the peripheral points of the character. Subsequently, some of n.times.m pixels of the character stored in a memory are repeated or removed as needed on the basis of the center position of the character to normalize the character to a size constituted by n.sub.0 33 m.sub.0 pixels.
As described above, according to the conventional method, many processing steps and long calculation time are required to enlarge or reduce one character constituted by a matrix of n.times.m pixels into a size of n.sub.0 .times.m.sub.0 pixels. As a result, the throughout of the computer for processing is degraded.